Anastacio, P. | bioRxiv Science

bioRxiv2025

A test of long-term and dose-dependent effects of fluoxetine exposure on the velocity of the invasive crayfish Procambarus clarkii

Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), is one of the most detected antidepressants in wastewater, managing to enter watersheds where it is taken up by freshwater fauna. Here we asked if the serotonergic system affects the dispersal capabilities of Procambarus clarkii, a prolific worldwide invasive freshwater crayfish species, thanks in part due to its dispersal rates. For this, we exposed adult crayfish to fluoxetine (serotonin facilitator) and para-chlorophenylalanine (PCPA, serotonin inhibitor) at two concentrations, and measured their velocity after 8 and 16 days, on a two-meter-long metal gutter. Overall, our treatment effects revealed to be non-significant, however the lowest dosage of fluoxetine seem to decrease crayfish mean velocity between the 8th and 16th day of exposure, thus shedding some light on the putative importance of the long-term exposure to environment dosage-dependent fluoxetine in modulating the dispersal capabilities of P. clarkii. Though further research is needed, these results can help us better understand the impact of ambient fluoxetine to this invasive species.

neuroscience↗

bioRxiv2025

The role of social-environmental factors on Procambarus clarkii dispersion capabilities

Procambarus clarkii is a prominent example of a successful invasive species, and its ability to disperse is known to be a key characteristic. The ability to disperse dictates the spread and impacts an invasive species has, with various known factors influencing it, such as temperature and circadian rhythms. However, there is still limited information on how crayfish social interactions influence their dispersion, and even already known factors still require further investigation. As such, the goal of this study is to deepen the knowledge of the Procambarus clarkii dispersion capabilities. To achieve this, two laboratory experiments were conducted to address the crayfish dispersal abilities, namely their speed, under controlled conditions. The first experiment tested the effect of the interaction of two temperatures (16{degrees}C and 22{degrees}C) and the presence or absence of food in a fully lit or darkened room. The second experiment tested the effects of pairing individuals of the same and opposite sex and of different and/or similar sizes. Three velocity values were obtained: the first considered the crayfishs final position on the track, the second considered the crayfishs furthest point on the track, and finally, the third considered the total distance travelled by the crayfish. Results show that when exposed to the higher temperature and in the absence of food, crayfish increased their speed, but size and sex did not seem to have an effect overall. When paired, female crayfish that were behind another crayfish achieved faster speeds on average than males in the same position. We also found that smaller females had faster velocities when paired with bigger females than with bigger males. The observed increase in speed with higher temperatures suggests that, in the face of current global and habitat changes, P. clarkiis rate of spread may accelerate. However, if provided with a reliable food source, crayfish may disperse less. Still, more research is needed to expand our understanding of which factors contribute to P. clarkiis dispersion capabilities, as this may prove important in formulating new plans and strategies to limit its impacts.

animal behavior and cognition↗